To increase the range-finding distance despite these atmospheric losses, the following routes are available:                increase the energy per pulse, but this increase is limited by ocular safety constraints and by the volume of the emitter which increases with the energy per pulse,        increase the size of the reception pupil but this increases the dimensions of the system,        increase the sensitivity of the receiver with multi-pulse systems that use micro-lasers or fiber optic lasers. This makes it possible to use post-integration. There is an increase in the average power (energy per pulse×rate) without increasing the energy per pulse.        
Currently, three main laser range-finder categories can be distinguished:                range-finders with modulated continuous emission        multi-pulse range-finders        single-pulse range-finders.        
The range-finders that have modulated continuous emission are used either with cooperative targets or when the measurement time is not critical. A cooperative target is, for example, equipped with a retroreflector, and thus returns more light.
For long distances (>10 km), the range-finders normally use a single high-energy pulse limited by ocular safety in conditions of use, that is to say, less than 100 mJ and for a wavelength of between 1.5 and 1.8 μm. This energy, depending on the applications, ranges from a few millijoules to a few tens of millijoules per pulse.
The multi-pulse range-finders are used for short distances (<10 km) with post-integration. To reduce the cost, the emission from a laser diode is used.
The post-integration presents certain drawbacks.
Thus, it should be recalled that:                if, for an emitted pulse, SNR is the detected echo,        then, for n pulses emitted we have (nS)/(n 1/2 N), or (n 1/2 S)/N, hence an improvement by a factor n 1/2.        
However, in the case of post integration, the pulse repetition frequency limits the distance that can be reached because of the distance ambiguity. This ambiguity occurs when a detected pulse originates either from the last pulse emitted, returned by a near target, or from a pulse emitted previously and returned by a distant target, without there being any way of determining which target is measured between these 2 alternatives.
One solution applied by radars to eliminate this ambiguity consists in using a variable pulse repetition frequency (or rate): the variable time interval between two pulses makes it possible to carry out the accumulation (post-integration) despite this ambiguity to the detriment of an increase in the level of noise in which the ambiguous echoes are buried. However, in the case of optical pulses, reception which is sensitive to the emission wavelength can be disturbed by the backscattering of the atmosphere and by the echoes of the short-distance emissions.
Another solution consists in waiting long enough for a pulse to return before emitting the next pulse. The distance to be taken into account can be greater than the guaranteed maximum range. A target forming a retroreflector can provide an echo that can be detected well beyond the expected maximum range. This means not exceeding a pulse repetition threshold frequency, called threshold frequency, to avoid having ambiguities. For example, for a range of 75 km, the round-trip duration of a signal is approximately 500 μs; in this case, the threshold frequency is therefore 2 kHz. If an integration time of 1 second is acceptable, it is then possible to accumulate 2000 measurements, or an increase in SNR by a factor 44 (square root of 2000), which is significant. For this reasoning to be valid, the target must be sufficiently stationary throughout the measurement duration.